Mybatis工具类

一.工具类 

package util;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.InputStream;

public class MyBatisUtil {
    //获得SqlSession工厂
    private static SqlSessionFactory factory;
    //创建ThreadLocal绑定当前线程中的SqlSession对象
    private static final ThreadLocal THREAD_LOCAL = new ThreadLocal();

    static {
        try {
            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            factory = new SqlSessionFactoryBuilder().build(is);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //获得连接（从THREAD_LOCAL中获得当前线程SqlSession）
    private static SqlSession openSession(){
        SqlSession session = THREAD_LOCAL.get();
        if(session == null){
            session = factory.openSession();
            THREAD_LOCAL.set(session);
        }
        return session;
    }

    
    public static void closeSession(){
        SqlSession session = THREAD_LOCAL.get();
        session.close();
        THREAD_LOCAL.remove();
    }

    
    public static void commit(){
        SqlSession session = openSession();
        session.commit();
        closeSession();
    }

    
    public static void rollback(){
        SqlSession session = openSession();
        session.rollback();
        closeSession();
    }



    
    public static  T getMapper(Class clazz){
        SqlSession session = openSession();
        return session.getMapper(clazz);
    }
}

二.自动装备等级

全等级匹配多表联查映射文件可不用写对应列，只要写association标注实体类即可，建议每次自动加上全等级匹配节省代码

三.缓存

存在内存中的临时数据

一级缓存（session级别，也称本地缓存）不能跨session

 结果： 同一个session只会执行一次sql语句 

 二级缓存：全局缓存namespace级别

核心配置文件加入

映射配置文件加入

实现类实现Serializable接口

要记得关闭session，不然会进入一级缓存

四.注解

可直接使用注解在Mapper接口写sql语句，后面直接调用即可

public interface PhoneMapper {
    @Delete("delete from phone where pid=#{id}")
    public int delete(int id);
    @Insert("insert into phone values(default,#{pname},#{pcolor},#{price},#{b.bid})")
    public int insert(Phone p);
    @Select("select * from phone where pid=#{id}")
    public Phone fid(int id);
    @Update("update phone set pname=#{pname},pcolor=#{pcolor},price=#{price} where pid=#{id}")
    public int update(@Param("pname") String pname, @Param("pcolor")String pcolor,@Param("price") String price, @Param("id")int id);